Changes in Flood Risk and Perception in Catchments and Cities (HS01 – IUGG2015) Proc. IAHS, 370, 69–74, 2015 proc-iahs.net/370/69/2015/ Open Access doi:10.5194/piahs-370-69-2015 © Author(s) 2015. CC Attribution 3.0 License. Two-dimensional hydrodynamic flood modelling for populated valley areas of Russian rivers V. V. Belikov1, I. N. Krylenko1,2, A. M. Alabyan2, A. A. Sazonov2, and A. V. Glotko3 1Water Problems Institute, Moscow, Russia 2Lomonosov Moscow State University, Moscow, Russia 3Akvarius Research and Production LLC, Moscow, Russia Correspondence to: I. N. Krylenko ([email protected]) Received: 17 March 2015 – Accepted: 17 March 2015 – Published: 11 June 2015 Abstract. Results of flood modelling for three cities located in different parts of Russia: (1) Veliky Ustyug at the Northern Dvina river (Europe); (2) Mezhdurechensk at the Tom river (Siberia); and (3) Blagoveschensk at the Amur river (Far East) are presented. The two-dimensional hydrodynamic model of flow in channels and on floodplain STREAM_2D on the basis of the numerical solution of two-dimensional Saint–Venant equations on a hybrid curvilinear quadrangular and rectangular mesh was used for the simulations. Verification of the model through a comparison of simulated inundated areas with outlines of flooded zones from satellite images for known hydrologic situations demonstrate close correspondence (relative errors of 7–12 % in terms of the area for peaks of the analysed floods). Analyses of embankment influence of large-scale levees on the water flow demonstrate that, in some cases, water levels could rise by more than 1 m and the patterns of the flooding zones could significantly differ. 1 Introduction under the name “STREAM_2D”. The model has been ap- plied to flooding simulation in numerous key areas on the There are more than 700 cities and towns, thousands of vil- great Russian rivers: the Volga, the Amur, the Ob, the Lena, lages and settlements, and more than seven million hectares etc. (Zaitsev et al., 2004), including the modelling of flooding of agricultural land of the Russian territory are exposed to a zones in the case of dambreaks of the main reservoirs. risk of flooding. The loss from the biggest floods, such as the Detailed information about the topography of the region extraordinary flood in the Amur basin in 2013, amounts to and the river bed relief is necessary for model setup. Water tens of billion rubles. The total annual damage from flooding discharges and water levels at the modelling area boundaries in Russia reaches 100 billion rubles (Frolov, 2013). Floods are utilized as the model input. As a result of modelling one often are followed by losses of human life, as was the case in can determine the flooded areas and obtain a spatial distribu- the city of Krymsk in 2002 and 2012. tion of flow velocities, water surface levels and depths at any One of the ways for decreasing flood damage is reasonable point of the channel and the inundated floodplain. planning of floodplain developments, taking into account possible characteristics of flooding for different scenarios of development and protection simulated by hydrodynamic models. A two-dimensional hydrodynamic model for chan- 2 Study areas nel and floodplain flow has been developed by V. V. Belikov and colleagues since the 1990s. It is based on approaches of In this paper we present the results of flood modelling of pop- irregular hybrid computational meshes and original methods ulated parts of river valleys in three cities located in different of interpolation (Belikov and Semenov, 1988, 2000). Several parts of Russia: (1) Veliky Ustyug at the Northern Dvina river previous modifications to the computational modules (named (Europe); (2) Mezhdurechensk at the Tom river (Siberia); and RIVER, BOR and FLOOD) are now upgraded and integrated (3) Blagoveshchensk at the Amur river (Far East) (Fig. 1a). Published by Copernicus Publications on behalf of the International Association of Hydrological Sciences. 70 V. V. Belikov et al.: Two-dimensional hydrodynamic flood modelling Figure 1. Case study areas: (a) overall location, (b) Veliky Ustug at the Northern Dvina, (c) Mezdurechensk at the Tom river, (d) Blagovesh- ensk at the Amur river. The city of Veliky Ustyug with a population of about 30 thousand is situated in the northern part of European Russia at the confluence of the Sukhona and the Yug rivers (Fig. 1b), and where the Northern Dvina river originates from their junction. It is an ancient Russian city founded in 13th cen- tury. During all its history the city was flooded repeatedly. The floods are due to snow melting and ice jams. Ice jams may cause more than 2 m additional water level rise. The last large flood was observed here in May 1998, when more than half of the city and nearby territories were inundated. A sig- nificant flood took place also in April 2013. In this paper we use this case for exploring some specific features concerning the levee efficiency. The city of Mezhdurechensk is situated in West Siberia on the Tom river at its confluence with the Usa river (Fig. 1c). Its population is about 100 000. The city was founded in the middle of the 20th century as the Siberian centre of the mining industry. The system of levees with a total length of more than 15 km protects Mezhdurechensk from floods. Figure 2. Modelling grid configuration for the Mezhdurechensk After the big flood in 1977 when the levees were practi- city area. cally overtopped, they were reconstructed and their height was increased. River valleys near the city are rather narrow – about 2 km. The discharge of 1 % exceedance probability of the Tom and the Usa rivers at the junction are 3640 and even higher than the discharge of 1 % exceedance probability 2730 m3 s−1, respectively. The maximum observed discharge – 4340 m3 s−1. of the Tom river during the flood in May 1977, which was in- The third case study is the city of Blagoveshchensk duced by snow melting and additional rainfall, was evaluated (Fig. 1d) with a population of about 200 thousand. It is sit- uated in the Far East of Russia at the Amur river (at the Proc. IAHS, 370, 69–74, 2015 proc-iahs.net/370/69/2015/ V. V. Belikov et al.: Two-dimensional hydrodynamic flood modelling 71 confluence of the Amur and the Zeya rivers). The Russian- f D λwjwj=2, λ is the hydraulic resistance (roughness) co- Chinese state boundary passes along the Amur river between efficient. Blagoveshchensk and Chinese city of Heihe. Floods here are This system of shallow water Eqs. (1) and (2) belongs to rain induced. The most significant occurred in 1958, when the type of quasilinear hyperbolic systems and is obtained by levees were broken and part of the city was flooded; and in averaging the three-dimensional non-stationary equations of 1984, when the streets near the river were inundated. In 2013 Reynolds over the stream depth assuming hydrostatic vertical the entire Amur basin suffered from flooding, and water lev- distribution of pressure. els near Blagoveshchensk raised by more than 9 m. The city For solving the system of the Eqs. (1) and (2) the cor- was not flooded significantly due to appropriate defence con- responding initial and boundary conditions are needed. At structions, but other nearby settlements were flooded. The an initial point in time t D 0: w (x;y;0) D w0 (x;y) and floodplains of the Zeya and the Amur just below the conflu- h(x;y;0) D h0 (x;y). Boundary conditions are established ence have widths of more than 10 km. Discharges of 1 % ex- along the borders of the modeled area, for example, water ceedance probability of the Amur and the Zeya rivers at their discharge, water level or no flow conditions. junction are 16 700 and 12 800 m3 s−1, respectively. Such discharges were observed in August 1984. During the last flood of 2013, the sum of the maximum discharges of Amur 4 Input data and methodology of modelling and Zeya at the confluence was slightly lower, with a max- imum discharge of 12 500 m3 s−1 for the Amur and a maxi- Detailed information about the topography of the floodplains mum discharge of 13 300 m3 s−1 for the Zeya. was used for model setup. Maps of scales 1 V 25 000 and 1 V 10 000 were digitized for the Tom and Dvina rivers flood- plains. Double satellite images WorldView-1 were utilized 3 Mathematical and numerical model of flow as input data of floodplain relief of the Amur river near dynamics Blagoveschensk. Data of the riverbed relief, flow velocities, water discharges, and water surface slopes were obtained The basis of the mathematical two-dimensional model con- from detailed field surveys organised by the Lab of soil ero- sists of the non-stationary equations of Saint–Venant also sion and river channel processes of the Geography Faculty of known as “the shallow water equations”. They are widely Lomonosov Moscow State University. used in computing the hydraulics of open channels (Cunge et The discretization of the modelling area in STREAM_2D al., 1980). These equations consider the main forces operat- consists of an irregular hybrid computational mesh. We used ing on a stream with a free surface (gravity, friction, pressure curvilinear quadrangular grids with a spatial resolution from and inertia; Coriolis’s force and wind influence can be con- about 10 × 30 to 40 × 100 m for the river channels and linear sidered in addition), and the three-dimensional orography of constructions (such as roads, levees) on the floodplains. The the land surface. other territories were covered by triangular grid cells with The system of the Saint–Venant equations in an integrated irregular spatial resolution from 50 to 300 m depending on divergent form (i.e.